Polymeric nanoparticles (NPs) are attractive drug delivery vehicles. Various forms of the NPs have been studied for the delivery of chemotherapeutic agents to treat cancer. In these polymeric NPs, chemotherapeutic agents are either encapsulated in polymer matrices or covalently conjugated to polymers via hydrolysable or enzymatically degradable linkages. Systemically administered NPs are ideally able to bypass the recognition of the reticuloendothelial system (RES), extravasate at the leaky tumor vasculatures, penetrate and homogeneously distribute in solid tumor tissues, get internalized by the target cancer cells, penetrate cellular and subcellular membranes, and then release their drug cargo in the cytoplasma of the target cancer cells in a sustained manner. NPs that can successfully overcome all these systemic, tissue, and cellular barriers are urgently needed. In addition to these translational barriers, NPs must be able to be stored for periods of time before clinical use. Many NPs aggregate in solution or in a lyophilized state. Aggregation can destroy the utility of these compositions by making them unable to accomplish one or more of the previously mentioned objectives. Accordingly, there is a need for NPs that can be prepared, stored, and systemically administered without aggregation.